1. Field of the Invention
The present invention relates to semiconductor devices and a manufacturing method thereof, and more particularly, to a semiconductor device having an insulation film on a conductive layer, and a manufacturing method thereof.
2. Description of the Background Art
Reducing the size of interconnections and providing multilayers thereof are now required to further increase the integration density of semiconductor integrated circuit devices. It is necessary to insert an interlayer insulation layer between each interconnection to provide a multilayer structure of the interconnections. If the surface of this interlayer insulation layer is not planar, a stepped portion will be generated at the interconnection formed above the interlayer insulation film. This causes defects such as disconnection.
Therefore, the surface of the interlayer insulation film (the surface of the device) must be made as flat as possible. The technique to planarize the surface of the device is called planarization. This planarization technique has become important in reducing the size and providing multilayers of the interconnection.
An SOG (Spin On Glass) film is known as an interlayer insulation film commonly used in planarization. Research of this SOG film is particularly in progress in the planarization technology taking advantage of fluidity of the material of the interlayer insulation film.
An xe2x80x9cSOG filmxe2x80x9d is a generic term of a film mainly composed of a solution in which a silicon compound is dissolved in an organic solvent, and silicon dioxide (SiO2) formed from that solution.
In forming an SOG film, first a solution having a silicon compound dissolved in an organic solvent is applied on a substrate in droplets. The substrate is rotated. By this rotation, the solution coating is provided on the substrate formed of interconnections so as to alleviate the stepped portion thereon. More specifically, the coating is formed thick at the concave portion and thin at the convex portion on the substrate. Thus, the solution coating is planarized at the surface.
Heat treatment is then applied to vaporize the organic solvent. Also, polymerization proceeds to result in a planarized SOG film at the surface.
An SOG film is typically classified into an inorganic SOG film that does not include any organic component of a silicon compound, as represented by the following general formula (1), and an organic SOG film including an organic component in a silicon compound, as represented by the following general formula (2).
[SiO2]nxe2x80x83xe2x80x83(1)
[RxSiOY]nxe2x80x83xe2x80x83(2)
(n, X, Y: integer; R: alkyl group or aryl group)
Inorganic SOG contains a great amount of moisture and a hydroxyl group. The inorganic SOG has a disadvantage that it is more brittle than a silicon oxide film formed by CVD (Chemical Vapor Deposition). For example, a crack is easily generated during heat treatment in an inorganic SOG film when thicker than 0.5 xcexcm.
In contrast, an organic SOG film has the generation of a crack during heat treatment suppressed. The organic SOG film can be formed having a thickness of approximately 0.5-1.0 xcexcm. The usage of an organic SOG film allows the formation of an interlayer insulation film that is greater in film thickness. Therefore, sufficient planarization can be achieved for even a great stepped portion on a substrate.
Although superior in planarization, an inorganic SOG film may adversely affect the metal interconnection and the like since it contains a great amount of moisture and a hydroxyl group. There is a possibility of degradation in the electric characteristics, corrosion, and the like. This problem may similarly be encountered in an organic SOG film including, though smaller in amount than the inorganic SOG film, moisture and a hydroxyl group.
Therefore, when an SOG film is employed as an interlayer insulation film, an insulation film such as a silicon oxide film formed by plasma CVD, for example, having the property of blocking moisture and hydroxyl groups as well as having high insulation and mechanical strength is generally provided above or below the SOG film.
A silicon oxide film formed by plasma CVD is superior in water resistance than an SOG film. However, it was conventionally difficult to obtain satisfactory water resistance effect even when a silicon oxide film formed by plasma CVD is applied. It was therefore difficult to improve reliability of a semiconductor device such as insulation characteristics while also improving planarization in conventional art.
An object of the present invention is to improve planarization as well as reliability of a semiconductor device.
Another object of the present invention is to achieve superior planarization and insulation characteristics in a semiconductor device.
A further object of the present invention is to easily manufacture a semiconductor device superior in planarization and insulation characteristics in a manufacturing method of a semiconductor device.
According to an aspect of the present invention, a semiconductor device includes a first insulation film, and a film for substantially preventing intrusion of impurities into a conductive layer. The first insulation film is formed on the conductive layer, and includes impurities. The film preventing intrusion is formed between the first insulation film and the conductive layer. By forming the first insulation film including impurities on the conductive layer, the first insulation film is modified to have the moisture and the hydroxyl group reduced. The first insulation film becomes less hygroscopic. Therefore, the water resistant ability of the first insulation film is improved. By using an SOG film, for example, as the first insulation film, both planarization and water resistance can be improved. Furthermore, the provision of a film between the first insulation film and the conductive layer effectively prevents the impurities of the first insulation film from entering the conductive layer. The disadvantage of a shorter electromigration lifetime of the conductive layer before disconnection due to intrusion of the impurities of the first insulation layer into the conductive layer can be prevented. The film for preventing intrusion can include at least one material selected from the group consisting of silicon oxide, silicon nitride, Ti, TiN, W, WNX and TiW. A second insulation film may be included between the first insulation film and the conductive layer. The second insulation film can be formed to include a film that is less hygroscopic than the first insulation film. Also, the first insulation film may include silicon oxide containing at least 1% of C (carbon). The first insulation film may further include an inorganic SOG film. The impurities may include at least one element selected from the group consisting of argon, boron, nitrogen, and phosphorus. The upper surface of the first insulation film may be planarized.
According to a method of manufacturing a semiconductor device of another aspect of the present invention, a first insulation film is formed on a conductive layer on a substrate. Impurities are introduced into the first insulation film. Prior to formation of the first insulation film, a film for preventing intrusion of impurities of the first insulation film into the conductive layer is formed on the conductive layer. According to the manufacturing method of a semiconductor device of the present aspect, first insulation film is modified by introducing impurities into the first insulation film. As a result, the moisture and the hydroxyl group included in the first insulation film are reduced. The first insulation film is now less hygroscopic. Thus, a first insulation film superior in water resistance can be obtained. By using an SOG film as the first insulation film, planarization is also improved. Thus, a semiconductor device that can be improved both in planarization and water resistance can be manufactured. By providing a film between the conductive layer and the first insulation film, intrusion of impurities from the first insulation film into the conductive layer can be prevented effectively. Therefore, the disadvantage of the impurities entering the conductive layer to adversely affect the lifetime thereof can be prevented. The film for preventing intrusion can be formed including at least one material selected from the group consisting of silicon oxide, silicon nitride, Ti, TiN, W, WNX and TiW. In the above-described structure, a step can be included of forming a second insulation film on the conductive layer and the film preventing intrusion prior to the step of forming the first insulation film. In this case, the second insulation film can include a film less hygroscopic than the first insulation film. Also, a step can be included of forming a third insulation film on the first insulation film after the step of implanting impurities into the first insulation film. The first insulation film can include silicon oxide consisting at least 1% of C, or an inorganic SOG film. Impurities can be introduced by ion implantation. The impurities can include at least one element selected from the group consisting of argon, boron, nitrogen, and phosphorus.
In a method of manufacturing a semiconductor device according to a further aspect of the present invention, a conductive layer is formed on a substrate. On the conductive layer, a film is provided including at least 1 material selected from the group consisting of silicon oxide, silicon nitride, Ti, TiN, W, WNX and Tiw for substantially preventing intrusion of impurities implanted from above of the conductive layer into the conductive layer. The conductive layer and the intrusion prevention film are patterned. A first insulation film is formed on the patterned conductive layer and intrusion prevention film. Impurities are implanted into the first insulation film. This implantation of impurities into the first insulation film on the patterned conductive layer provides the advantage of improving the water resistance of the first insulation film. The provision of the intrusion prevention film on the conductive layer prevents intrusion of impurities into the conductive layer even when impurities are implanted into the first insulation film. The problem of a shorter electromigration lifetime for the conductive layer (a Shorter Mean Time To Failure) caused by intrusion of the impurities into the conductive layer can be eliminated. Furthermore, planarization of the first insulation film is improved by employing an SOG film, for example, as the first insulation film. Thus, a semiconductor device can easily be manufactured that allows improvement of both planarization and water resistance.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.